//
// Created by weijing on 18-9-18.
//

#include "md5.h"
#include "memory.h"

static const sky_uchar_t *sky_md5_body(sky_md5_t *ctx, const sky_uchar_t *data, sky_usize_t size);


void
sky_md5_init(sky_md5_t *ctx) {
    ctx->a = 0x67452301;
    ctx->b = 0xefcdab89;
    ctx->c = 0x98badcfe;
    ctx->d = 0x10325476;

    ctx->bytes = 0;
}


void
sky_md5_update(sky_md5_t *ctx, const sky_uchar_t *data, sky_usize_t size) {
    sky_usize_t used, free;

    used = (sky_usize_t) (ctx->bytes & 0x3f);
    ctx->bytes += size;

    if (used) {
        free = 64 - used;

        if (size < free) {
            sky_memcpy(&ctx->buffer[used], data, size);
            return;
        }

        sky_memcpy(&ctx->buffer[used], data, free);
        data = (sky_uchar_t *) data + free;
        size -= free;
        (void) sky_md5_body(ctx, ctx->buffer, 64);
    }

    if (size >= 64) {
        data = sky_md5_body(ctx, data, size & ~(size_t) 0x3f);
        size &= 0x3f;
    }

    sky_memcpy(ctx->buffer, data, size);
}


void
sky_md5_final(sky_md5_t *ctx, sky_uchar_t result[16]) {
    sky_usize_t used, free;

    used = (sky_usize_t) (ctx->bytes & 0x3f);

    ctx->buffer[used++] = 0x80;

    free = 64 - used;

    if (free < 8) {
        sky_memzero(&ctx->buffer[used], free);
        (void) sky_md5_body(ctx, ctx->buffer, 64);
        used = 0;
        free = 64;
    }

    sky_memzero(&ctx->buffer[used], free - 8);

    ctx->bytes <<= 3;
    ctx->buffer[56] = (sky_uchar_t) ctx->bytes;
    ctx->buffer[57] = (sky_uchar_t) (ctx->bytes >> 8);
    ctx->buffer[58] = (sky_uchar_t) (ctx->bytes >> 16);
    ctx->buffer[59] = (sky_uchar_t) (ctx->bytes >> 24);
    ctx->buffer[60] = (sky_uchar_t) (ctx->bytes >> 32);
    ctx->buffer[61] = (sky_uchar_t) (ctx->bytes >> 40);
    ctx->buffer[62] = (sky_uchar_t) (ctx->bytes >> 48);
    ctx->buffer[63] = (sky_uchar_t) (ctx->bytes >> 56);

    (void) sky_md5_body(ctx, ctx->buffer, 64);

    result[0] = (sky_uchar_t) ctx->a;
    result[1] = (sky_uchar_t) (ctx->a >> 8);
    result[2] = (sky_uchar_t) (ctx->a >> 16);
    result[3] = (sky_uchar_t) (ctx->a >> 24);
    result[4] = (sky_uchar_t) ctx->b;
    result[5] = (sky_uchar_t) (ctx->b >> 8);
    result[6] = (sky_uchar_t) (ctx->b >> 16);
    result[7] = (sky_uchar_t) (ctx->b >> 24);
    result[8] = (sky_uchar_t) ctx->c;
    result[9] = (sky_uchar_t) (ctx->c >> 8);
    result[10] = (sky_uchar_t) (ctx->c >> 16);
    result[11] = (sky_uchar_t) (ctx->c >> 24);
    result[12] = (sky_uchar_t) ctx->d;
    result[13] = (sky_uchar_t) (ctx->d >> 8);
    result[14] = (sky_uchar_t) (ctx->d >> 16);
    result[15] = (sky_uchar_t) (ctx->d >> 24);

    sky_memzero(ctx, sizeof(*ctx));
}


/*
 * The basic MD5 functions.
 *
 * F and G are optimized compared to their RFC 1321 definitions for
 * architectures that lack an AND-NOT instruction, just like in
 * Colin Plumb's implementation.
 */

#define F(x, y, z)  ((z) ^ ((x) & ((y) ^ (z))))
#define G(x, y, z)  ((y) ^ ((z) & ((x) ^ (y))))
#define H(x, y, z)  ((x) ^ (y) ^ (z))
#define I(x, y, z)  ((y) ^ ((x) | ~(z)))

/*
 * The MD5 transformation for all four rounds.
 */

#define STEP(f, a, b, c, d, x, t, s)                                          \
    (a) += f((b), (c), (d)) + (x) + (t);                                      \
    (a) = (((a) << (s)) | (((a) & 0xffffffff) >> (32 - (s))));                \
    (a) += (b)

/*
 * SET() reads 4 input bytes in little-endian byte order and stores them
 * in a properly aligned word in host byte order.
 *
 * The check for little-endian architectures that tolerate unaligned
 * memory accesses is just an optimization.  Nothing will break if it
 * does not work.
 */
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define SET(_n)      (*(sky_u32_t *) &p[(_n) << 2])
#define GET(_n)      (*(sky_u32_t *) &p[(_n) << 2])
#else
#define SET(_n)                                 \
    (block[_n] =                                \
    (sky_u32_t) p[(_n) << 2] |                  \
    ((sky_u32_t) p[((_n) << 2) + 1] << 8) |     \
    ((sky_u32_t) p[((_n) << 2) + 2] << 16) |    \
    ((sky_u32_t) p[((_n) << 2) + 3] << 24))

#define GET(_n)      block[_n]*/
#endif


/*
 * This processes one or more 64-byte data blocks, but does not update
 * the bit counters.  There are no alignment requirements.
 */

static const sky_uchar_t*
sky_md5_body(sky_md5_t *ctx, const sky_uchar_t *data, size_t size) {
    sky_u32_t a, b, c, d;
    sky_u32_t saved_a, saved_b, saved_c, saved_d;
    const sky_uchar_t *p;
#if __BYTE_ORDER != __LITTLE_ENDIAN
    sky_u32_t       block[16];
#endif

    p = data;

    a = ctx->a;
    b = ctx->b;
    c = ctx->c;
    d = ctx->d;

    do {
        saved_a = a;
        saved_b = b;
        saved_c = c;
        saved_d = d;

        /* Round 1 */

        STEP(F, a, b, c, d, SET(0), 0xd76aa478, 7);
        STEP(F, d, a, b, c, SET(1), 0xe8c7b756, 12);
        STEP(F, c, d, a, b, SET(2), 0x242070db, 17);
        STEP(F, b, c, d, a, SET(3), 0xc1bdceee, 22);
        STEP(F, a, b, c, d, SET(4), 0xf57c0faf, 7);
        STEP(F, d, a, b, c, SET(5), 0x4787c62a, 12);
        STEP(F, c, d, a, b, SET(6), 0xa8304613, 17);
        STEP(F, b, c, d, a, SET(7), 0xfd469501, 22);
        STEP(F, a, b, c, d, SET(8), 0x698098d8, 7);
        STEP(F, d, a, b, c, SET(9), 0x8b44f7af, 12);
        STEP(F, c, d, a, b, SET(10), 0xffff5bb1, 17);
        STEP(F, b, c, d, a, SET(11), 0x895cd7be, 22);
        STEP(F, a, b, c, d, SET(12), 0x6b901122, 7);
        STEP(F, d, a, b, c, SET(13), 0xfd987193, 12);
        STEP(F, c, d, a, b, SET(14), 0xa679438e, 17);
        STEP(F, b, c, d, a, SET(15), 0x49b40821, 22);

        /* Round 2 */

        STEP(G, a, b, c, d, GET(1), 0xf61e2562, 5);
        STEP(G, d, a, b, c, GET(6), 0xc040b340, 9);
        STEP(G, c, d, a, b, GET(11), 0x265e5a51, 14);
        STEP(G, b, c, d, a, GET(0), 0xe9b6c7aa, 20);
        STEP(G, a, b, c, d, GET(5), 0xd62f105d, 5);
        STEP(G, d, a, b, c, GET(10), 0x02441453, 9);
        STEP(G, c, d, a, b, GET(15), 0xd8a1e681, 14);
        STEP(G, b, c, d, a, GET(4), 0xe7d3fbc8, 20);
        STEP(G, a, b, c, d, GET(9), 0x21e1cde6, 5);
        STEP(G, d, a, b, c, GET(14), 0xc33707d6, 9);
        STEP(G, c, d, a, b, GET(3), 0xf4d50d87, 14);
        STEP(G, b, c, d, a, GET(8), 0x455a14ed, 20);
        STEP(G, a, b, c, d, GET(13), 0xa9e3e905, 5);
        STEP(G, d, a, b, c, GET(2), 0xfcefa3f8, 9);
        STEP(G, c, d, a, b, GET(7), 0x676f02d9, 14);
        STEP(G, b, c, d, a, GET(12), 0x8d2a4c8a, 20);

        /* Round 3 */

        STEP(H, a, b, c, d, GET(5), 0xfffa3942, 4);
        STEP(H, d, a, b, c, GET(8), 0x8771f681, 11);
        STEP(H, c, d, a, b, GET(11), 0x6d9d6122, 16);
        STEP(H, b, c, d, a, GET(14), 0xfde5380c, 23);
        STEP(H, a, b, c, d, GET(1), 0xa4beea44, 4);
        STEP(H, d, a, b, c, GET(4), 0x4bdecfa9, 11);
        STEP(H, c, d, a, b, GET(7), 0xf6bb4b60, 16);
        STEP(H, b, c, d, a, GET(10), 0xbebfbc70, 23);
        STEP(H, a, b, c, d, GET(13), 0x289b7ec6, 4);
        STEP(H, d, a, b, c, GET(0), 0xeaa127fa, 11);
        STEP(H, c, d, a, b, GET(3), 0xd4ef3085, 16);
        STEP(H, b, c, d, a, GET(6), 0x04881d05, 23);
        STEP(H, a, b, c, d, GET(9), 0xd9d4d039, 4);
        STEP(H, d, a, b, c, GET(12), 0xe6db99e5, 11);
        STEP(H, c, d, a, b, GET(15), 0x1fa27cf8, 16);
        STEP(H, b, c, d, a, GET(2), 0xc4ac5665, 23);

        /* Round 4 */

        STEP(I, a, b, c, d, GET(0), 0xf4292244, 6);
        STEP(I, d, a, b, c, GET(7), 0x432aff97, 10);
        STEP(I, c, d, a, b, GET(14), 0xab9423a7, 15);
        STEP(I, b, c, d, a, GET(5), 0xfc93a039, 21);
        STEP(I, a, b, c, d, GET(12), 0x655b59c3, 6);
        STEP(I, d, a, b, c, GET(3), 0x8f0ccc92, 10);
        STEP(I, c, d, a, b, GET(10), 0xffeff47d, 15);
        STEP(I, b, c, d, a, GET(1), 0x85845dd1, 21);
        STEP(I, a, b, c, d, GET(8), 0x6fa87e4f, 6);
        STEP(I, d, a, b, c, GET(15), 0xfe2ce6e0, 10);
        STEP(I, c, d, a, b, GET(6), 0xa3014314, 15);
        STEP(I, b, c, d, a, GET(13), 0x4e0811a1, 21);
        STEP(I, a, b, c, d, GET(4), 0xf7537e82, 6);
        STEP(I, d, a, b, c, GET(11), 0xbd3af235, 10);
        STEP(I, c, d, a, b, GET(2), 0x2ad7d2bb, 15);
        STEP(I, b, c, d, a, GET(9), 0xeb86d391, 21);

        a += saved_a;
        b += saved_b;
        c += saved_c;
        d += saved_d;

        p += 64;

    } while (size -= 64);

    ctx->a = a;
    ctx->b = b;
    ctx->c = c;
    ctx->d = d;

    return p;
}